Cardiovascular diseases (CVD) are the major cause of death and disability in the United States and other industrialized countries despite recent declines in CVD mortality rates, They account for more deaths annually than any other disease, including all forms of cancer combinedi. In the USA more than 1 million heart attacks occur each year and more than half a million people still die as a result. This enormous toll has focused attention on the possible prevention of CVD by various means, especially through lowering of plasma cholesterol levels. It is well established now that elevated total cholesterol, and in particular low-density lipoprotein (LDL) cholesterol, in plasma plays an important role in the development of atherosclerosisii. Clinical trials have demonstrated clearly that decreasing cholesterol concentrations in plasma can contribute to primary and secondary prevention of coronary events and mortality.iii Some studies have estimated a 2% reduction in risk of a coronary artery event by a 1% reduction of total serum cholesterol.iv 
i Levi, R. I., Declining Mortality in Coronary Heart Diseases, Artherosclerosis, 1981, 1, 312-325. 
ii Cholesterol Adult Treatment Panel: Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Cholesterol in Adults, Arch. Intern. Med., 1988, 148,36-69. 
iii Frick, M. H., et al., Primary prevention Trial with Gemfibrozil in Middle-aged Men with Dyslipidemia: Safety of Treatment, Changes in Risk Factors, and Incidence of Coronary Heart Disease. New Engl, J. Med, 1987, 317, 1237-1245. Pederson T. R. et al., Randomised Trial of Cholesterol Lowering in 4444 Patients with Coronary Heart Disease: The Scandinavian Simvastatin Survival Study (4S), The Lancet, 1994, 344, 1193-1389. 
iv La Rosa, J. C, et al., The Cholesterol Facts: A Summary of the Evidence relating to Dietary Fats, Serum Cholesterol and Coronary Heart Disease: A Joint Statement by the American Heart Association and the National Heart, Lung and Blood Institute, Circulation, 1990, 81, 1721-1733. Law, M. R. et al, By how much and how quickly does Reduction in Serum Cholesterol Concentrations lower Risk of Ischemic Heart Disease? Br. Med. J., 1994, 308, 367-373. 
Serum cholesterol levels can for example be lowered by a daily intake of some components similar to cholesterol. The components similar to cholesterol reduce the absorption of cholesterol from the intestines into the bloodstream.
U.S. Pat. No. 5,958,913 discloses a substance comprising a sawed sterol fatty acid ester capable of lowering LDL cholesterol levels in serum and which is fat soluble. The substance can be taken orally as a food additive, food substitute or supplement A daily consumption of saturated sterol fatty acid ester in an mount between about 0.2 and about 20 g/day has been shown to reduce the absorption of endogenic cholesterol.
Alternatively, compositions that inhibit the cholesterol biosynthesis, for example by inhibiting enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), an enzyme involved in the cholesterol biosynthesis, can lower blood serum cholesterol by slowing down the production of cholesterol. It is believed that inhibition of HIMG-CoA reductase results in a reduction in hepatic cholesterol synthesis and intracellular cholesterol stores, a compensatory increase in low-density lipoprotein (LDL) receptors, and a subsequent enhanced removal of LDL-cholesterol from plasma. Potent inhibitors of HMG-CoA reductase include for example the compounds referred to as statins, which family comprises for example lovastatin, pravastatin and fluvastatin.
Several studies suggested a HMG-CoA reductase iniibiting effect of plant extracts. Wang et al.v demonstrated HMG-CoA reductase inhibition by several aqueous plant extracts in isolated rat hepatic microsomal preparations. In vivo studies on rats demonstrated the inhibitory effect of traditional Chinese herbs on the cholesterol biosynthesisvi.
v Wang, S. L. et al, Effects of Flos Chrysanthemum and several other Chinese herbs on in vitro HMGR activity of liver microsome of rast. Chinese J. of biochemistry, 1988, 4(6): 517-522. 
vi Wang S. L. et al, Effects of Flos Chrysanthemum and other fourteen Chinese herbs on metabolism of cholesterol in rats. Chinese J. of biochemistry, 1987, 3(4):319-323. 
An enzyme involved in the cholesterol metabolism (conversion of cholesterol into other components) is cholesterol 7α-hydroxylase. Hepatic cholesterol 7α-hydroxylase catalyses the conversion of cholesterol into 7α cholesterol, which is believed to be the rate limiting step in conversion of cholesterol into bile acids. It has been suggested that the increase of cholesterol 7α-hydroxylase activity results in the decrease of blood serum cholesterol and thus is an important pathway of elimination of cholesterol from the body. Methods for treatment of blood serum cholesterol related disorders by inhibition of cholesterol 7α hydroxylase are known in the art.
WO 91/15213 discloses a method for treatment of cholesterol gallstones employing side-chain hydroxylated cholesterol derivative. In particular the method for treatment of cholesterol gallstones involves ale administration of 25- or 26-hydroxycholesterol, which enhance the activity of cholesterol 7α-hydroxylase, thereby inhibiting for example cholesterol precipitation. Additionally, Wang et al.vi showed that several herbal preparations are capable of increasing cholesterol 7α hydroxylase activity.
According to Raicht et al.vii, feeding cholesterol to rats increased cholesterol absorption from 1.2 to 70 mg/day and inhibited its synthesis in the liver and enhanced conversion of cholesterol to bile acids from 13.7 to 27.3 mg/day. Furthermore, when given cholesterol to the rats, HMG-CoA reductase activity was inhibited 80%. With beta-sitosterol, cholesterol absorption was inhibited but cholesterol synthesis was increased from 20.0 to 28.8 mg/day.
vii Raicht, R. F et al., Sterol balance studies in the rat. Effects of diet cholesterol and beta-sitosterol on sterol balance and ate-limiting enzymes of sterol metabolism. Biochimica et Biophysica Acta, 1975, 388(3): 374-384. 
The majority of cholesterol lowering compositions currently known in the art include ingredients which either lower cholesterol absorption within the intestines or inhibit cholesterol biosynthesis, e.g., by inhibition of HMG-CoA reductase. As Raicht et al.vii demonstrated, the inhibition of cholesterol absorption in the intestine (using β-sitosterol) lowers cholesterol absorption, however, the inhibition of cholesterol absorption in the intestines is followed by an increase in HMG-CoA reductase activity. Increase of the HMG-CoA reductase activity is likely to increase cholesterol biosynthesis and thereby reduce the net effect of cholesterol absorption inhibitors. It is therefore desirable to decrease serum cholesterol levels using combination compositions, which reduce cholesterol absorption within the intestine and additionally inhibit cholesterol biosynthesis, e.g. by inhibiting HMG-CoA reductase activity,
Methods of reducing plasma cholesterol levels comprising administering a combination of an effective amount of cholesterol biosynthesis inhibitor and an effective amount of cholesterol absorption inhibitor are disclosed in U.S. Pat. No. 5,661,145. The administered combination includes a beta-lactam cholesterol absorption inhibitor and a HMG-CoA reductase inhibitor, which can for example be a statin, for example lovastatin or pravastatin. Other pharmaceutical combination compositions including certain cholesterol absorption inhibitors and cholesterol synthesis inhibitors useful for the treatment of hypercholesterolemia and atherosclerosis are described in U.S. Pat. No. 5,807,834.
WO 98/01759 describes a method of determining in animal the ratio of serum campesterol to the level of β-sitosterol comprising several steps. Additionally, a combination composition for enhancing in an animal the inhibitory effect of phytostrols on cholesterol enterocyte absorption, which comprises one or more phytosterols which inhibit predominantly one or both of cholesterol and beta sitosterol and one or more compounds which limit cholesterol synthesis, e.g. compounds selected form HMG CoA reductase inhibitors, for example lovostatin, is described. Further described is the main disadvantage of the above composition i.e. the use of statins, and the critical side effects related with the use of statins.
WO 00/15201 discloses a composition for preventing and treating CVD containing phytosterols or phytostanols as agents inhibiting cholesterol absorption and tocotrienols as agents suppressing cholesterol biosynthesis.
WO 00/38725 provides combinations of cardiovascular therapeutic compounds for the prophylaxis or treatment of cardiovascular disease including hypercholesterolemia and atherosclerosis. Combinations disclosed include an ileal bile acid transport inhibitor combined with a cholesteryl ester transport protein inhibitor, a fibric acid derivative, a nicotinic acid derivative, a microsomal triglyceride transfer protein inhibitor, a cholesterol absorption antagonist, or others. Further combinations include a CETP inhibitor with a fibric acid derivative, a nicotinic acid derivative, a bile acid sequestrant, a microsomal triglyceride transfer protein inhibitor, a cholesterol absorption antagonist, or others.
U.S. Pat. No. 5,958,417 describes a herbal combination comprising Crataegus, Ho Shou Wu, Cassia Seed, Chrysanthemum, Lotus Leaf, Alisma, Hu-Zhang, and Rhubarb wherein the herbs are present in specific weight percentages. However, the herbal combination lacks a potent cholesterol absorption-inhibiting component, such as an effective amount of phytosterol and/or phytostanol.
Notwithstanding these disclosures, there remains a need in the art for compositions for use in reduction of blood serum cholesterol levels or prevention of elevated blood serum cholesterol levels. Combination compositions including cholesterol absorption inhibitors and cholesterol synthesis inhibitors useful for reduction of blood serum cholesterol levels known in the art are mostly chemically manufactured compositions and the known compositions are therefore undesirable for many people, not natural and costly.
Additionally, the combination compositions known in the art cannot be used frequently for a longer period since negative side effects will occur. Recent studies have indicated that drugs like statins, often used as HMG-CoA reductase inhibitors in combination compositions, and fibrates can be carcinogenic or cause other undesirable side effects. Newman et alviii reported that all members of the classes stains and fibrates cause cancer in rodents. Furthermore, two hyperlipidemic patients treated with simvastatin, a potent inhibitor of HMG-CoA reductase, experienced cheilitis after beginning treatment The rash resolved after discontinuation of medication and subsequent treatment with topical moisturizers and topical corticosteroids (Mebregan et al.ix). Khosla et alx alerts clinicians to the possible adverse effect of simvastati and other statins by reporting a case of a 79-year-old man who had onset of fatigue, myalgia, and pleuritic chest pain 3 months after initiation of therapy with simvastatin. Lovastatin was reported to cause liver failure (Tolmanxi).
viii Newman et al., Carcinogenicity of lipid-lowering drugs. JAMA, 1996275(1): 55-60. 
ix Mehregan D. R. et al., Cheilitis due to treatment with simvastatin. Cutis, 1998, 62(4):197-198. 
x Koshla R. et al, Simvastatin-induced lupus erythematosus. South Med J., 1998, 91(9):873-874. 
xi Tolman K. G., Defining patient risks from expanded preventive therapies. Am, J. Cardiol, 2000, 85(12A): 15E-9E. 
Furthermore, combination compositions known in the art to date only comprise effective amounts of at most two of the blood serum cholesterol reducing activities, selected from reduction of cholesterol absorption in the intestine, inhibition cholesterol of biosynthesis and increase of cholesterol metabolism.